Molecular dynamics simulations of the effects of carbon dioxide on the interfacial bonding of polystyrene thin films

Abstract

Fabrication of nanoscale polymer‐based devices, especially in biomedical applications, is a challenging process due to requirements of precise dimensions. Methods that involve elevated temperature or chemical adhesives are not practicable due to the fragility of the device components and associated deformation. To effectively fabricate devices for lab‐on‐a‐chip or drug delivery applications, a process is required that permits bonding at low temperatures. The use of carbon dioxide (CO2) to assist the bonding process shows promise in reaching this goal. It is now well established that CO2 can be used to depress the glass transition temperature (Tg) of a polymer, allowing bonding to occur at lower temperatures. Furthermore, it has been shown that CO2 can preferentially soften a polymer surface, which should allow for effective bonding at temperatures even below the bulk Tg. However, the impact of this effect on bonding has not been quantified, and the optimal bonding temperature and CO2 pressure conditions are unknown. In this study, a molecular dynamics model is used to examine the atomic scale behavior of polystyrene in an effort to develop understanding of the physical mechanisms of bonding and to quantify how the process is impacted by CO2. The final result is the identification of a range of CO2 pressure conditions which produce the strongest bonding between PS thin films at room temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011

Interatomic Potential for Hydrocarbons on the Basis of the Modified Embedded-Atom Method with Bond Order (MEAM-BO)

“…The e k are expansion parameters for the triple bond increments. The β bond (0, 1,3) are the exponential decay factors for the D(z) function and bond increment function. The p bond (0, 1,3) are the power in the D(z) function.…”

“…The β bond (0, 1,3) are the exponential decay factors for the D(z) function and bond increment function. The p bond (0, 1,3) are the power in the D(z) function. 2. obtain the remaining C parameters using the direct grid search method and the downhill simplex method for the target elastic constants of the diamond cubic structure and the energies of carbon phases.…”

“…, δ H a 5. iterate steps 1 through 4 for further improvement. 6. adjust β H (1) for the pressures of the dense systems β H…”

“…11. adjust β 2 (1) , β 2 (1) double bond parameters to correct the elastic constants for graphene β 2 (1) , β 2…”

Reduced-order molecular-dynamics model for polystyrene by equivalent-structure coarse graining

“…An overall thickness of approximately 40 nm may provide adequate length scale effects in the simulation system to yield an acceptable degree of reliability in the molecular models [2].…”